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EM231 Thermocouple Module Problems

Created by: camo at: 3/3/2009 7:50 AM (7 Replies)

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3/3/2009 7:50 AM	Rate (0)
camo Posts: 6 Rating: (0)	Hello all. I am having some trouble getting good readings from an em231 thermocouple module. I am using a CPU 224 XP with 7 expansion modules. I have (in order) slot 0 CPU 224XP DC/DC/DC slot 1 EM 231 4 analog in slot 2 EM 235 4 analog in 1 analog out slot 3 EM 222 4 digital out slots 4, 5, 6 EM 232 4 analog out slot 7 EM 231 Thermocouple module. I have 3 J type thermocouples connected to the device with the last input shorted and all dip switches set to 0. They are standard mineral insulated thermocouples bought from RS Australia. I have checked my connections and earthing many many times and they are by the book. When i run the program at an ambient temperature of about 21 degrees C i get a reading of around 230 which is close. When i cool the room where the thermocouples are installed to about 4 degrees the reading goes up (very slowly) to about 270 to 290. When i heat the thermocouples up with my hands i can get them up to about 430 very quickly. So i seem to be able to get the reading to go up if i either heat them or cool them. Does anyone know if i have to use a special type of thermocouple for this module, or if the position of the thermocouple module in relation to the CPU makes a difference. Any help would be greatly appreciated.
camo Posts: 6 Rating: (0)
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3/3/2009 8:48 AM	Rate (0)
Helmut_13 Posts: 2930 Rating: (432)	Hi, try disabling the analog filter for your TC channels. Do you have shielded wires for your TC's? Do you have power wires in parallel to the TC sensor wires? Grounding of the TC's only at the Module side? Hope this helps
Helmut_13 Posts: 2930 Rating: (432)
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3/8/2009 2:34 PM	Rate (0)
camo Posts: 6 Rating: (0)	Hello I have done all of that, shielded cables, away from power lines, no analog fintering, but i have grounded the thermocouples to the panel earth, not at the thermocouple module. I will give that a go. I havent been able to get out to the site to try it this week. Thank you for your advice.
camo Posts: 6 Rating: (0)	Last edited by: camo at: 3/8/2009 2:36 PM
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3/10/2009 10:17 AM	Rate (0)
camo Posts: 6 Rating: (0)	Hello Helmut I have been back to the site and checked all of those things. I earthed the shield of the cable to the module site instead of the panel and still the same problems. Any other thoughts? i have racked my brain for ages trying to figure out how to get it to work. What method would you use to sense air temperature. I am nervous to go out and buy more parts in case it was a simple error of mine. I now have shielded cable running to the thermocouple, bundled only with sensor wires, the thermocouple casing is connected with the shield of the cable which is connected straight to the thermocouple module (it doesnt go through duct or anything in the panel). Not sure what to do. Thank you for your help
camo Posts: 6 Rating: (0)
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3/17/2009 1:20 PM	Rate (0)
Oscar_83PL Bronze Member Joined: 10/22/2008 Last visit: 9/10/2025 Posts: 377 Rating: (5)	How much did you lengthen the cables? Maybe problem is somewhere in the middle? One more thing. What is your setings of dip switches for EM231?
	Last edited by: Oscar_83PL at: 3/17/2009 1:24 PM
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3/19/2009 1:47 AM	Rate (0)
fqiang Posts: 23 Rating: (0)	How long is the wire? If I do not foget, the line must be less than 100 meters. I prefer to use RTU . I used to use Intelligent Digital Transmitter Controller to convert to 0-20ma or 4-20for Em231 (not TC Type). By the way ,Did you use compensation wire for the thermocouple?
fqiang Posts: 23 Rating: (0)
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4/1/2009 8:46 PM	Rate (0)
madw Regular Member Joined: 6/22/2008 Last visit: 9/2/2025 Posts: 10 Rating: (1)	When you use normal copper extension wires the reading at 20 degrees will be normal 200. At higher temperatures the output will be incorrect. Use thermocouple extension wire and connect it direct to your TC module.

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4/1/2009 11:47 PM	Rate (0)
Helmut_13 Posts: 2930 Rating: (432)	Hi, change the possition of the DIP5 and see if the direction is still wrong. I heard of TC modules with different DIP positions. Regards Helmut
Helmut_13 Posts: 2930 Rating: (432)
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